Conventionally, in 3GPP (3rd Generation Partnership Project), a radio access system and a radio network which achieve higher-speed data communication (hereinafter referred to as “LTE-A (Long Term Evolution-Advanced)” or “A-EUTRA (Advanced Evolved Universal Terrestrial Radio Access)”.) have been discussed utilizing evolution of a radio access system and a radio network of cellular mobile communication (hereinafter referred to as “LTE (Long Term Evolution)” or “SUTRA (Evolved Universal Terrestrial Radio Access)”), and a more broadband frequency band than the LTE.
In the LTE, an OFDM (Orthogonal Frequency Division Multiplexing) system, which is multicarrier transmission, is used as a communication system for radio communication from a base station apparatus to a mobile station apparatus (downlink). In addition, an SC-FDMA (Single-Carrier Frequency Division Multiple Access) system, which is single career transmission, is used as a communication system for radio communication from the mobile station apparatus to the base station apparatus (uplink).
In an uplink of the LTE, the base station apparatus determines radio resource allocation, a coding rate, and a modulation scheme of a PUSCH, which is a channel for data transmission, by utilizing a reference signal for measuring an uplink channel (an SRS (Sounding Reference Signal)) which is transmitted by the mobile station apparatus.
In the uplink of the LTE, TPC (Transmit Power Control) is performed for the purpose of suppressing power consumption of the mobile station apparatus, and reducing given interference to other cells. Shown is a formula used to determine a transmit power value of the SRS specified in the LTE.[Formula 1]PSRS(i)+min{PCMAX,PSRS—OFFSET+10 log10(MSRS)+PO—PUSCH+α·PL+f(i)}  (1)
In Formula (1), PSRS(i) indicates a transmit power value of the SRS in an i-th subframe. min {X, Y} is a function for selecting a minimum value of X and Y. PO—PUSCH is a transmit power as the basis of the PUSCH, and is a value specified by a higher layer. PSRS—OFFSET is an offset indicating a difference of transmit powers as the basis of the PUSCH and that of the SRS, and is a value specified by the higher layer. MSRS indicates the number of PRBs (Physical Resource Blocks), which is a unit for allocation of a radio resource used for SRS transmission, etc., and indicates that a transmit power becomes larger as the number of PRBs used for SRS transmission increases.
In addition, PL indicates a path loss, and α is a coefficient multiplied to the path loss and is specified by the higher layer. f is an offset value (TPC value by a closed loop or an open loop) calculated based on a TPC command transmitted by DCI (Downlink Control Information). In addition, PCMAX is a maximum transmit power value, and may be a physical maximum transmit power or may be specified by the higher layer.
In the LTE-A, it is required that the LTE-A has backward compatibility with the LTE, i.e., a base station apparatus of the LTE-A is able to simultaneously perform radio communication with both a mobile station apparatus of the LTE-A and a mobile station apparatus of the LTE, and that the mobile station apparatus of the LTE-A is able to perform radio communication with both the base station apparatus of the LTE-A and the base station apparatus of the LTE, and it has been discussed that the LTE and the LTE-A use a same channel structure.
Non-Patent Document 1 has proposed to introduce a technology in which a mobile station apparatus transmits an SRS only once in addition to periodic SRS transmission when requested to transmit the SRS by a base station apparatus in order to improve accuracy of the SRS in the LTE-A. Hereinafter, an SRS which a conventional mobile station apparatus transmits periodically is referred to as a periodic SRS, and an SRS which the conventional mobile station apparatus transmits only once when requested to transmit the SRS by the base station apparatus is referred to as an aperiodic SRS (or a one shot SRS, a scheduled SRS). Specifically, the base station apparatus performs setting of a radio resource regarding the aperiodic SRS to the mobile station apparatus in addition to setting of a period and radio resources (a frequency band and a cyclic shift) regarding the periodic SRS, includes an indicator requesting an SRS in DCI to be transmitted via a PDCCH, and transmits the DCI to the mobile station apparatus.
When the SRS is requested by the indicator, the mobile station apparatus transmits the SRS only once in accordance with the setting regarding the aperiodic SRS.